My sister slept with the light on until she was 27. She rightfully blames me.My sister slept with the light on until she was 27. She rightfully blames me.

I would leap out of closets with my hands made into claws. I would shut off the lights when she was in the bathroom. I would creep up behind her in a demon mask and tap her on the shoulder, and when she twisted around she would scream and then laugh and then hit me.

She had a collection of troll dolls. The ones with the bug eyes and the wild hair. And I would move them around, sneaking one under her pillow, another in her sock drawer, and when she asked if I did it, I would give her a dead-faced look and say, "What are you talking about?" One time I snuck into her room late at night and rearranged the troll dolls, all 20 of them, in a line next to her bed. When she woke the next morning she found them staring at her, one of them carrying a note that read, "BAD DREAMS," with the R and the S backwards (for trollish authenticity).

I invented an elaborate mythology about the roof people. They were lost souls, I said, caught in a kind of purgatory. They lived in attics and on roofs. They were jealous of the living, and if they could find ways to trick us, to hurt us, they would. At night I would crawl out onto the roof and scratch at her window and then scramble back to my room so that I was sitting at my desk by the time she arrived there in an angry panic.

We're both writers now. My novel Red Moon is a more elaborate, grown-up version of me leaping out of the closet with my hands made into claws. And her first book, Demon Camp, which releases in 2014, is a nonfiction account of... well... it sort of defies a quick summary. Let's just say there are exorcisms involved.

Be afraid of the Percys. We've been playing in the dark and filing our fangs for years, training for this moment. In a way, we turned out to be the roof people.

Benjamin Percy has won a Whiting Writers' Award, a Plimpton Prize, two Pushcart Prizes, and a grant from the National Endowment for the Arts. He is the author of the novels Red Moon and The Wilding, and two short story collections.

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